1. Field of the Invention
My invention is in the field of packaging systems, and particularly relates to systems for quickly and easily preparing delicate articles for shipment.
My invention is particularly suited to situations in which the number of shipments anticipated for articles of a given type does not justify molding preformed shipping liners of impact-absorbing material such as polystyrene foam. Such situations encompass one-of-akind shipments, and also anticipated shipments of up to a few hundred units, the exact cutoff point being of course dependent upon the relative value and fragility of the items being shipped.
2. Prior Art
There are four principal forms of protection for fragile shipments: molded polystyrene containers, padded envelopes, container inserts, and loose fill.
Polystyrene containers are molded to form-fit the merchandise. They have the advantage of securing the contents snugly within an outer package, and of being crushable in event of impact, whereby the energy of impact is permanently absorbed and the contents thus protected. However, expensive molding equipment and molds are involved, and such expense can be justified only by a large number of articles to be shipped. This large number in turn requires considerable storage space for the bulky empty containers. If the containers are purchased outside the packaging facility, then shipping problems can arise because of the high bulk and low weight. Fire risk in storage and shipping can also be a problem.
Padded envelopes are either laminated pulverized paper, bonded-plastic air bubbles, or bonded-plastic foam. These envelopes are preferable only in that they need not be expensively custom-made for each article to be shipped, but they provide little or no protection against stress, strain or compression. There is generally insufficient distance between the contents and the exterior surface of the envelope, and the merchandise generally can move in at least certain directions within the envelope. In some designs, when the outer cover is punctured the padding falls away.
Container inserts are categorized in two main styles, flexible and rigid. The flexible style is a plastic foam such as flexible polyurethane or polyethylene, or a chemical which is inserted directly into the container in liquid form and chemically induced to expand to fill all the unused space with foam. Inserts in the rigid category, such as die-cut paperboard, wooden forms, and various plastic parts, act as protection. Flexible inserts are quite expensive, use excessive storage space, and are a fire hazard. In particular, the chemically-expanded liquid types require considerable skill and care of use, to protect the merchandise around all of its sides and to provide the optimum amount of material density within the package. Proper cushioning depends critically on that density, and in turn upon the amount of material placed within a container in relation to the unused space therein. As such foam remains truly flexible and resilient, it of course acts as a spring to store impact energy and later release it, rather than permanently absorbing the energy. Therefore the protective effect is limited to cushioning, that is, softening and distributing, impact--rather than permanently absorbing the impact. When the stored energy is released the resulting "second impact" within the package can sometimes be quite damaging. Rigid inserts have some of the same disadvantages of cost and storage requirements, offer little or no protection against impact at the point of support of an insert itself, and require assembly time prior to shipping.
Loose fill includes small polystyrene shapes, newspapers, excelsior, sawdust, and the like. Such fill is extremely bulky, settles in transit lessening the protection provided, constitutes a fire hazard in storage, and is time-consuming to use.
U.S. Pat. No. 3,503,177 to Kropscott et al., issued Mar. 31, 1970, describes a system for holding and cushioning fragile articles in shipment; this system involves controlled reexpansion of polystyrene beads carried and restrained within air-permeable plastic bags. The beads are first expanded in the fashion customary in the expandable-polystyrene art, and then partially collapsed, sealed in a flexible bag, e.g. of polyethylene, that permits slow diffusion of air through its walls and into contact with the shrunken beads. As air diffuses through the walls of the bags and walls of the cells of the shrunken beads they reinflate; in the meantime the bag is placed within a container surrounding articles to be shipped, so that the reinflating particles support and protect the article. This system serves a useful purpose, but is limited in application to shipping situations wherein the initial expansion, shrinking and bagging of the styrene beads can be carried out at the same site as the final packing steps. The relatively short life of the shrunken stage of the polystyrene beads is the principal reason for this limitation. According to the disclosure of Kropscott et al., the life can be extended by providing additional, air-tight packaging of the bagged, shrunken beads; this might permit shipment of the beads in their shrunken state, subject to the necessity of maintaining each bag in an air-tight condition until within an hour of its final use. Various inconveniences and risks of such a technology will be apparent, except in relatively large-scale operations capable of justifying machinery and technicians for preparing the shrunken beads on-site just before use. In addition, the method of Kropscott et al. involves the use of additional boxing or other external containers, which must themselves be sealed and secured as separate operations after the bagged polystyrene beads are placed under and around the article to be shipped.
U.S. Pat. No. 3,667,593 to Pendleton, issued June 6, 1972, discloses a flowable packing material, used loose, consisting of multiple discrete plastic pods with air trapped within each. Closing an overfilled package presses pods in around a packed article. This art is subject to the general objections mentioned above for loose fill.
U.S. Pat. No. 2,709,856 to Hunter and Phillips, issued June 7, 1955, furnishes an example of radio-frequency power use for final preparation of a finished package. Here however the application is simply drying of yarn inside a package after liquid processing of the yarn; no cushioning material or polystyrene is involved or suggested.
U.S. Pat. Nos. 2,998,501 (Aug. 29, 1961) and 3,242,238 (Mar. 22, 1966) to Edberg and Immel, and 3,104,424 (Sept. 24, 1963) to Immel introduce methods and apparatus for making foamed polystyrene articles with radio-frequency irradiation as the means of injecting energy to heat and expand the polymer. These basic patents disclose introduction of wetting agent to the polystyrene beads from which the articles are to be made, to provide for uniform coating of a high-power-factor material (such as water) onto the beads. This in turn permits uniform heating and expansion of the polymer by a radio-frequency electric field.
U.S. Pat. No. 3,253,064 to Buonaiuto, issued May 24, 1966, discloses details of the molding process for radio-frequency heating. This patent also incidentally explains the use of a "blowing agent": this is a gas-generating substance or a fugacious liquid, also sometimes termed a "propellant," which is incorporated within the granular or bead or pellet original form of the polystyrene, and which expands the granules or beads or pellets under the application of heat by being released or thermally expanded (or both) at the same time the polystyrene is softening under the same application of heat. The pressure of the thermally expanding blowing agent expands the styrene into the desired foam structure, given only that the heat energy required to soften the resinous material and to release and expand the blowing agent is supplied--either externally generated, or generated within the polymer by radio-frequency irradiation as mentioned earlier.
None of these patents discloses or suggests a unitary prefabricated package of the character described below, or of course any of the essential refinements to such a package which are also disclosed hereunder.